1. Technical Field
The present invention relates to sheet conveyance in image reproducing apparatuses such am electrostatographic printers and copiers; in particular, the present invention relates to portions of the sheet conveyance system in such image-reproducing apparatuses that are operator-accessible for maintenance such as clearing sheet jams.
2. Description of Related Art
Image reproducing devices such as electrostatographic copying machines, printers and facsimile devices, are equipped with a sheet conveyance system for conveying sheets in transport from the sheet supply section of the apparatus through the image reproducing and finishing sections to a discharge or storage location.
To facilitate sheet removal in the event of sheet jams in such sheet conveyance systems, it in well known to make portions of the system withdrawable. For example, mechanism frames of the sheet conveyance system are designed to be withdrawable frontward (in terms of where an operator runs the machine).
Among such image reproducing devices are photocopiers capable of dual-sided printing, in which case the sheet conveyance system will have a section that turns over once-printed sheets and re-supplies them to the image-reproducing station which may be, for example, the photoconductive drum of electrostatographic devices. Herein it is also known to make such a dual-sided sheet handling section of the sheet conveyance system withdrawable for operator maintenance access.
Such a sheet conveyance system dual-sided sheet handling section comprises a main frame withdrawable frontward of the photocopier, an intermediate tray fitted to the main frame for storing sheets turned over therein in transport, and upper and lower conveyors disposed above the intermediate tray. Each of the conveyors has a conveying guide, one end of which is pivotably supported on the main frame, and conveying rollers rotatably fitted into the conveying guide. The conveying rollers of the upper and lower guides are disposed pressing on each other. Sheets in conveyance therein are thus pinched by opposing roller pairs and turned over and sent toward the intermediate tray.
In addition, the upper and lower conveying guides are joined by a linkage by which they are spaced apart in turning open the main frame. Therein, with the main frame withdrawn, when the free end of the upper conveying guide is grasped and rotated, the upper conveying guide is turned a predetermined amount, whereupon the lower conveying guide is subsequently brought into the turning movement.
In a sheet conveyance system of the above-described configuration, sheets may become jammed on the intermediate tray, and between the upper and lower conveyors. Hence, the conveyor pair is rotatably fit into the main frame, off and onto which the pair can be opened and closed.
That is, when a sheet jam occurs between the upper and lower conveyors, it can be cleared by drawing the main frame out of the photocopier, and grasping and lifting only the upper conveying guide in order to take out the sheet. Wherein a sheet jam occurs on the intermediate tray, however, the upper conveying guide must be lifted far enough to bring the lower conveying guide into the turning movement via the linkage, which then opens up the area over the intermediate tray so that the jammed sheet can be cleared. Accordingly, owing to the conveying guide pair linkage, wherein sheets have become jammed in either of the pair of regions they can be removed by only turning the upper conveying guide.
In the above-described conventional sheet conveyance system, owing to the linkage of the upper and lower conveying guides, sheet jams at the pair of locations can be dealt with by only lifting the upper conveying guide to turn open the dual-sided sheet handling section. Nevertheless, since the upper and lower conveying guides only swing on their link, if the hand lifting the upper conveying guide is removed, being that the upper conveying guide is urged towards the lower conveying guide side by gravity, the upper conveying guide will fall through the turn approaching the lower conveying guide. Consequently, wherein there is a sheet jam between the upper and lower conveying guides, a two-handed process becomes necessary--for example, while the upper conveying guide is held by the right hand, the jammed sheet is removed away by the left hand--such that the jammed sheet clearing process is cumbersome.